NASA scientists called the rock "Oileán Ruaidh," which is the Gaelic name for an island off the coast of northwestern Ireland. The rock is about 45 centimeters (18 inches) wide from the angle at which it was first seen on September 16.

"The dark color, rounded texture and the way it is perched on the surface all make it look like an iron meteorite," said science-team member Matt Golombek of NASA's Jet Propulsion Laboratory, Pasadena, Calif. Opportunity has found four iron meteorites during the rover's exploration of the Meridiani Planum region of Mars since early 2004. Examination of these rocks has provided information about the Martian atmosphere, as well as the meteorites themselves, NASA stated.

NASA recently said that Opportunity has reached the halfway point of a journey between two large craters on the red planet. NASA said since Opportunity left the area known as Victoria Crater two years ago this month, the rover has traveled about six miles of an almost 12 mile journey to the Endeavour Crater. At about 22 kilometers (14 miles) in diameter, Endeavour is about 28 times wider than Victoria.

Endeavor is of interest to scientists because NASA's Mars Reconnaissance Orbiter satellite has shown the crater to have clay minerals, the space agency stated. Clay minerals, which form exclusively under wet conditions, have been found extensively on Mars from orbit, but have not been examined on the surface.

The rover traveled 3.3 miles in 2009, farther than in any other year on Mars, NASA has noted. Overall Opportunity has driven more than 11 miles and returned more than 133,000 images. The rover has made numerous discoveries, including the first mineralogical evidence that Mars had liquid water, according to the space agency.

Cooney is an Online News Editor and the author of the Layer 8 blog, Network World's daily home for the not-just-networking news. He has been working with Network World since 1992. You can reach him at mcooney@nww.com.